1. Field of the Invention
The present invention relates to an apparatus for working a metal pipe to form an irregularity or a helical groove in an inner surface and/or an outer surface of the metal pipe.
2. Prior Art
A metal pipe such as copper pipe and aluminum pipe, for example, for use in heat-exchangers, is formed with an irregularity or a helical groove not only in an outer surface of the metal pipe, but also in an inner surface thereof, in order to improve heat transfer.
Referring to FIG. 1, a pipe working apparatus of the prior art for forming an irregularity or a helical groove in an inner surface of a metal pipe 1 is fundamentally arranged such that the metal pipe 1 is delivered axially of the pipe and is caused to pass through a drawing unit 2 which comprises a die 2a and a drawing plug 2b, so that the pipe is reduced in diameter so as to have predetermined wall thickness and diameter. A helical groove is formed in the inner surface of the diameter-reduced metal pipe 1 by a pipe working assembly 4 which comprises rolling rolls 5 in pressure contact with an outer surface of the metal pipe 1, and an inner surface working plug 6 floatingly disposed within the metal pipe 1 at a position corresponding to the rolling rolls 5. The rolling rolls 5 are rotatably supported by a ring-like support 7 through arms 8 of a driving mechanism (not shown) which revolves the rolling rolls 5 around the metal pipe 1, with respective axes of the rolling rolls 5 being inclined at a predetermined angle with respect to an axis of the metal pipe 1.
The pipe working apparatus of the kind described above has such advantages that it is possible to increase forming rate and working speed to improve productivity of the apparatus, and it is also possible to work metal pipes having considerable axial length.
With the pipe working apparatus, however, it is frequently required to adjust respective positions of the rolling rolls 5 dependent upon the wall thickness or diameter of the rolled metal pipe 1. In this regard, the pipe working apparatus of the prior structure has such problems that since the rolling rolls 5 are fixedly connected to the ring-like support 7 by means of the arms of the driving mechanism, it is difficult to adjust the respective positions of the rolling rolls 5 so that considerable time is required for the arrangement and setting of the apparatus, resulting in the deterioration of workability and operability. In addition, there is also a problem that because of the complexity in structure, the maintenance of the apparatus is troublesome.